Final diagnosis


Collar rot (Sclerotinia sclerotiorum)

A brown, moist canker tending to surround the stem, and a cottony, white mycelium can be observed. <b><i>Sclerotinia sclerotiorum</i></b>
The rot has gained almost the whole stem; black sclerosis can be observed on it. <b><i>Sclerotinia sclerotiorum</i></b>
A dark brown to brown lesion at the soil line surrounding a tobacco plant stem. <i><b>Sclerotinia sclerotiorum </b></i>(Sclerotinia rot)
During periods of high humidity, white, cottony mycelium grows over the rotten tissues and long black sclerotia develop also in the pith. <i><b>Sclerotinia sclerotiorum</b></i>
An important lesion is surrounding the tobacco stem. <i><b>Sclerotinia sclerotiorum</b></i>
<i>Sclerotinia sclerotiorum</i>
The fungus often begins in rotten leaves and petioles and moves from these into the stem causing moist, dark brown cankers. On the surface of cankers and inside the stem, one can observe white mycelium and sclerotia. <i><b>Sclerotinia sclerotiorum</b></i> (Sclerotinia leaf spot)
During the periods of wet weather <i>Sclerotinia sclerotiorum</i> (white mould, <i>Sclerotinia</i> rot) develops rapidly and massively on tobacco in the curing barn; it causes stem rot and leaf rot and produces several sclerotia.
<i>Sclerotinia sclerotiorum</i>
When the leaves become necrotic they turn beige to light brown and dry in texture. <i>Sclerotinia sclerotiorum</i> (<i>Sclerotinia<i/> leaf spot)
Half of this leaf has been colonised by the fungus; discrete white mycelial squads on the midrib can be observed. <i><b>Sclerotinia sclerotiorum </b></i>(Sclerotinia leaf spot)
A brown, moist rot has covered the lamina, several sclerotia and a white, felt like mycelium can be observed on the midrib. <i><b>Sclerotinia sclerotiorum</i></b> (Sclerotinia leaf spot)
<i><b>Sclerotinia sclerotiorum</b></i> (<i>Sclerotinia</i> leaf spot) is characterised by black sclerotia which it forms on and in the infected organs.
Aerial dispersal (wind dissemination) of the pathogen is mostly by ascospores produced in apothecia (small, dark beige to brown, trumpet-shaped structures) which can be found in and around tobacco fields. <i><b>Sclerotinia sclerotiorum</i></b> (<i>Sclerotinia</i> leaf spot)